I’ve previously printed custom lego pieces for the Lego League kids, that my wife has at work. I’m using a Creality Ender 3 S1 with 0.4mm nozzle. Though I’ve not tried smaller parts. They were 8x2 units and 2 or 3 units high. They have the name of the kid on the side. It took some tries to get the tolerances good enough, but now I can print them with normal speed and minimal post processing.
So I think it depends on what pieces you want to print.
An interesting customer base might be small communal organisations. At our local scouts troop I had a discussion with a friend, who is also in IT. His idea (not fleshed out) was to provide small local organizations with a stack of already configured open source software to support the typical needs of such organizations (like a wordpress website, a nextcloud for file storage and common calender, limesurvey for surveys and event registration, mailman3 for mailing lists,…). Depending on the needs you could sell the initial setup process (your personal work in setting up and skill transfer) or ongoing support. Though such organizations normally don’t have much money to give away. So probably its not really worth your time financially (though probably really appreciated in the community).